Papers by Keyword: Measurement

Abstract: Changes in the climate over the past decades have caused weather extremes that bring numerous unwanted phenomena. Many of these irregularities cause unusually high and low temperatures, intense droughts and devastating floods. All of the listed natural disasters caused by weather extremes affect a wide range of fields which are crucial for our everyday life and its quality. The most affected areas are health and safety, agriculture, industry, transportation. It is therefore evident that the effect of extreme weather in any form can bring not only financial loses, but also a loss of human lives. Based on these facts it is of great interest that the effects of these natural forces are minimised or totally eliminated. This paper deals with the performance of a newly designed mobile flood barrier in real simulated field test conditions. Construction of the barriers was designed solely by the Slovak University of Technology at its Faculty of Mechanical Engineering with the intention of providing effective, economic and safe flood barriers system with a short assembly time. The undertaken testing was focused on the performance of the flood barriers under static pressure by the deflection measurements. The testing consisted of the following steps: experiment design, on sight mounting and fine-tuning of the whole measuring apparatus and evaluation of the gathered data. To simulate real conditions which the barrier will experience during its use, a life size model of the flood barrier segment was constructed and tested. The measurement setup, measurement procedures, the outcomes of the deformation testing together with the resulting deflection model are presented in the following pages of this paper.

Abstract: Experimental and numerical analysis describes the design of noise removal effect of the friction pair of trapezoidal screw in a special device call Stick-Slip effect. Solution of the problems builds on previous measurements and testing sliding pairs, which was testing in last analysis. The pair worked in the special bath oil, its characteristics is that it does not support the mechanical lubrication. Measurements and calculations showed that it is necessary to enlarge the diameter for 32 kN load trapezoidal screw. This will reduce the contact pressure, which leads to polish the contact surfaces. You then slip together better and are not as easily stick slip effect.

Abstract: The monitoring of stiffened composite panels behavior using resistance strain gauges (SG), fibre optic Bragg grating sensors (FOBG) and contactless optical measurements based on digital image correlation (DIC) principle is discussed in the paper. Both the panel structure and different load cases are specified. Mechanical tests include different load-scenarios like static and fatigue loading in compression of reference and impacted panels. The main reason of failure is buckling. The measurements taken from the sensors captured all changes in the buckling modes of the panel. Moreover, they showed a good correlation between FOBG and SG strain measurements.

Abstract: This paper is focused on determination of load sharing in planetary transmission during the test and usual operation. Load sharing is one of examined items in transmission. That is investigation of power flow uniformity through satellites in planetary transmission.

Abstract: The fabrication of ultra-precision freeform surfaces possessing non-rotationally symmetric geometry and sub-micrometre form accuracy requires an efficient positioning method for precisely locating the position of the workpiece on the machine with high repeatability during the manufacturing cycle. This paper presents an initial attempt to develop a fiducial aided positioning (FAP) method for precisely locating the freeform workpiece on multi-axis machine tools in order to improve the accuracy and efficiency in the manufacturing of ultra-precision freeform surfaces. The FAP method makes use of fiducials to establish intrinsic surface features of the freeform workpiece which are used to determine the coordinate transformation between the coordinate frame of the workpiece and the machine in the machining process and the measurement process. A preliminary simulation experiment was conducted to verify the technical feasibility of the proposed FAP method. The results show that the FAP method is technically feasible to establish a link between the machining and measurement process so as to improve machining accuracy.

Abstract: Daylight factor is one of the physical parameters affecting indoor environmental. We can determine this factor in many ways. The main ways are computational methods, in situ measurements and finally measurements in architectural models. Measurements in models enable us comparison both measurements under real sky and under artificial sky. We can study changes in internal conditions - the colors and variability of the interiors and potential variability of window openings. Using of mini - photometer head in measurements enable us to give precision quality of design daylight in interior and validate computational methods for the real space.

Abstract: This article provides information about in-flight measurement of a small sport aircraft. The strain gauges were used as sensors for load monitoring on the nose landing gear structure. To obtain overall forces it was necessary to do the calibration procedure. After the calculation of strain gauge coefficients the equations for calculating of total force, total force direction and individual force components were determined. During test flights the data acquisition system was installed into the aircraft. The data from strain gauges were collected together with other flight parameters like speed, altitude and data from inertial measurement unit which determined the exact movements of the aircraft before landing. The data recorded during fifty-six flights were analysed to obtain loads acting in the aircraft structure. These results were compared with calculated values.

Abstract: This paper deals with a new experimental approach to the analysis of radial, axial, and tilt error movements of machine tool spindles under load. The main focus is on the identification of error spindle movements under different machine operation conditions between 500 - 5000 rev / min and loads in the range of 50 - 500 N. Errors of the spindle movements are measured on the cylindrical workpiece using capacitance sensors for different loads. The analysis of measurements of radial, axial, and tilt error movements of machine tool spindle indicates a dependency of loads and measured errors. The integration of error measurements into novel multi-body dynamic models of machine tool spindles is very important for prediction of machine behaviour during a cutting process and for prediction of workpiece geometric accuracy.

Abstract: This article deals with the long-term testing of experimental lightweight wall and comparison of the measurement with two different simulation software packages – WUFI and ESP-r in term of temperatures inside the fragments. Two lightweight timber-frame wall fragments with various outdoor coating colors were exposed to the real outdoor boundary climate conditions for four years. The indoor boundary conditions were secured as constant. In the wall fragments there are several built-in sensors.

Abstract: The article analyses the measurement with increased absorption kinetics of hydrogen into the La_0.85Ce_0.15Ni₅ alloy. Within a time interval of 180 s an amount of 0.142 kg (1.58 m³) of hydrogen was absorbed into 56 kg of alloy. The process of absorption was accompanied by an increased temperature of the bed. Therefore it was simultaneously cooled by a cooler using Peltier elements. The numerical calculation of non-stationary heat transfer within the bed was performed with a known amount of heat generated in the bed, known temperatures and flow rates. Simulation results allow us to determine temperature time paths at key points of the bed and give insight on the transient phenomena which occurs in the extreme load of the metal hydride (MH) bed. This allows establishing safe limits for the absorption of hydrogen into a particular alloy.